1. Field of the Invention
This invention relates generally to exercising equipment, and more particularly, but not by way of limitation, to exercising machines that utilize hydraulic systems to provide resistance to operator applied exercising force.
2. Description of the Prior Art
Today, good health is highly emphasized in our society. Proper maintenance of the cardiovascular system and various muscle groups requires a great deal of exercise. Weight lifting is a popular type of exercise that provides a very effective means to achieve and maintain good health.
The traditional method of weight lifting is "free" weight lifting. Free weight lifting is generally performed with barbells and dumbbells. Due to the danger and complexity involved, free weight exercises have been replaced to a large extent with exercises performed on exercise machines. Exercise machines provide more efficient ways to exercise and are much easier and safer to use.
An exercise machine operates by providing resistance to various exercising forces exerted or applied by the exerciser or machine operator. Most conventional exercise machines utilize adjustable weight stacks to provide the resistance.
Although machine weight lifting has many advantages over free weight lifting, conventional weight machines are not suitable in all applications. Most conventional machines are too expensive for the individual weight lifter to afford. It is often very burdensome, time consuming and dangerous for the operator to adjust the weights. The conventional weight machines are generally too heavy to be moved, and take up a great deal of space. The constant sound of clashing weights makes the machines too noisy for many environments.
In addition, conventional weight machines are not suitable for certain types of exercises. The weights provide both positive and negative resistance. Positive resistance is created when the weights are lifted or pushed. Negative resistance is created when the weights are lowered or released. For some types of exercises, particularly "rapid thrust" type exercises, the sudden transfer of supporting energy from one set of muscles to another created by a sudden change in resistance can cause muscular strains and other injuries.
To lessen some of the problems associated with conventional machines, various exercise machines have heretofore been developed which utilize hydraulic systems instead of weights to provide resistance to the various exercising forces applied by the machine operators. The resistance is created by restricting the flow of hydraulic fluid from one side of a piston to another. Some of the machines previously developed provide adjustable resistance to the exercising forces applied in one direction, but little or no resistance to forces applied in the opposite direction. This allows "rapid thrust" type exercises to be performed. See U.S. Pat. Nos. 4,241,913 and 4,480,832. The resistance to force applied in the one direction is created by passing the fluid through a restricted opening. When force is applied in the opposite direction, the fluid is allowed to freely flow around the restricted opening. By bypassing the fluid, the resistance is minimized or eliminated.
Many of the hydraulic exercise machines heretofore developed include complex conduit systems that are easily broken and hard to maintain. The resistance provided is often difficult or impossible to adjust. Only limited types of exercises can be performed on many machines.
Thus, there is a need for a simple hydraulic exercise machine that provides resistance to force applied in one direction, but little or no resistance to force applied in the opposite direction. There is a need for such a machine that allows a wide variety of exercises to be performed without taking up a great deal of space, and which is easy to adjust and safe to use.